Histopathological study of gills in experimentally amoebic gill disease (AGD) infected Atlantic salmon, Salmo salar, L.

Document Type : Full paper (Original article)


1 Department of Clinical Sciences, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran

2 Department of Aquaculture, Tasmanian Aquaculture and Fisheries Institute, University of Tasmania, Launceston, Australia


Amoebic gill disease (AGD) is the most important parasitic disease of Atlantic salmon industry in
Australia. Atlantic salmon (Salmo salar) experimentally infected with Neoparamoeba sp. apparently showed
AGD gross signs on the gill and an amoebic-associated gill pathology. Physico-chemical factors of water
during the experiment were monitored regularly and were approximately constant (temperature: 17oC,
salinity: 35 g/l, total ammonia: 0.25 mg/l, pH = 7.9). In this study significant gill pathology was observed
histologically, and in all of the sections a multifocal hyperplasia and fusion of adjacent secondary lamellae
was seen. The severity of pathological changes observed in the sections did not always correspond with the
number of amoebae and even occurred in the absence of amoebae. Some histopathological changes that were seen in the secondary lamellae are: thickening of the secondary lamellae due to hyperplasia, reduction in chloride cell density and an increase in mucous cell numbers of the epithelium. Some of neighboring
secondary lamellae was seen attached to one another, but entire fusion of the primary lamellae was not
observed. Amoebae were seen in all sections in significant densities mostly in the outer part of hyperplasic